1. Field
Example embodiments relate to semiconductor devices including a non-polar face, and/or methods of manufacturing the same.
2. Description of the Related Art
A semiconductor material grown in a heterojunction semiconductor thin film structure may be used to form optical or electrical devices by adjusting a lattice constant or a band gap of the semiconductor. A nitride semiconductor is an example of such a semiconductor material.
A nitride semiconductor is relatively stable both thermally and chemically, and also has a relatively wide direct transition band gap. Thus, a nitride semiconductor material is used to form electronic devices, such as heterojunction bipolar transistors (HBTs), high electron mobility transistors (HEMTs), metal semiconductor field effect transistors (MESFETs), etc. Nitride semiconductor materials are also used to form light-emitting devices, such as laser diodes (LDs) that generate light in a relatively short wavelength band, light-emitting diodes (LEDs), etc. In a more particular example, a nitride semiconductor material-based LED that generates blue or green light having a relatively short wavelength is a relatively high-output optical device that enables realization of various natural colors.
Conventionally, a nitride thin film (or layer) in a polar (0001) c-face direction is formed on a c-face sapphire substrate. However, due to an internal electric field, a quantum-confined stark effect (QCSE) occurs in the nitride thin film in the polar (0001) c-face direction. Thus, an internal quantum efficiency of the nitride thin film is relatively limited. In one alternative, a non-polar nitride optical element may be grown.
A non-polar GaN epitaxial layer using a hetero substrate, such as a sapphire substrate or a silicon-carbide (SiC) substrate, has a threading dislocation (TD) density of about 1010/cm2 and a relatively high basal stacking faults (BSF) density of about 105/cm2. The defect densities are several tens to several hundred times the defect density of an epitaxial layer when GaN is grown in a polar c-face direction. These defects function as non-emission portions and cause a reduction in quantum efficiency.
A thick sapphire substrate, epitaxial lateral overgrowth (ELO) and intermediate layer insertion have been explored in an effort to reduce these defects. However, processes associated with these alternatives are relatively complex, which increases costs and time.